This is a request for an ADAMHA Research Scientist Award (RSA). My research objectives concern two important issues concerning the biological bases of behavior: (i) the evolution of behavior and the changes the underlying neuroendocrine mechanisms undergo in the process, and (ii) how genes and environment interact in the development of behavior. The behaviors measured are species-typical "innate" behaviors. Perhaps the greatest barrier to fruitful investigation of the first issue is that representatives of ancestral species usually no longer exist. The whiptail lizards are a rare case in which representatives of both the ancestral and the descendant species still exist. By comparing the neuroendocrine mechanisms that control sexual behaviors in the descendant species with those of the ancestral species, the evolutionary process can be examined directly. The fundamental problem of the second issue is that behavior is the combined result of both nature and nurture. Is it possible to relate gene expression during embryogenesis to the display of specific behaviors during adulthood? In other words, how are quantitative events like gene expression orchestrated into qualitative events like behavior? In many reptiles sex is determined by the temperature of the incubating egg. I am tracing how the temperature signal is transduced into a biological signal that acts ultimately at the genetic level to channel sexual development. This also has enabled me to begin examining the role of temperature-induced gene expression in the development of the adult phenotype. The perspective taken is multidisciplinary, combining the integrating molecular, cellular, physiological, and organismal phenomena within an evolutionary view of biological organization. Further, this research is conducted both in the field and in the laboratory, because the field is a valuable testing ground for the adaptive functions of behavior whereas the laboratory is the only possible arena for determining the physiological and developmental bases of behavioral phenomena observed in the field. This approach permits both the causal mechanisms and the functional outcomes of species-typical behaviors to become evident within each level of biological organization in a way that illustrates the relations among the level. A renewal of the RSA will enable me to continue collaborations with colleagues both at the University of Texas and other institutions. It will enable me to continue my field work, which usually occurs during the academic year. By freeing me from the usual course load and administrative duties, I can devote the majority of my time to research. It allows me to serve as mentor to postdoctoral, graduate, and undergraduate students working on independent research projects. The RSA has allowed me to participate in programs of continuing education for high school science teachers and to provide laboratory experience for high school students.